Introduction The goal of this project is to identify the major molecular components of the adaptive response of Burkholderia pseudomalleiio reactive oxygen and nitrogen stress. B. pseudomallei is the causative agent of melioidosis. High mortality rates, difficult treatment regimens, and the wide availability of pathogenic strains have led to the classification of B. pseudomallei as a potential bioterrorism agent. More effective treatments and an efficacious vaccine are needed to defend against a B. pseudomallei attack. During the course of infection, intracellular pathogens must cope with a variety of host-mediated stress conditions, in particular, the antibacterial properties of phagocytic cells. B. pseudomallei invades and persists in macrophages. Macrophages produce antimicrobial reactive oxygen and nitrogen species (ROS and RNS). Mechanisms by which intracellular pathogens avoid these antibacterial agents are central to their survival during infection. Genes involved in resistance to ROS that are present in the B. pseudomallei genome include the oxyR and soxR genes, and the genes for superoxide dismutases, catalases, and alkyl hydroperoxide reductases. Our working hypotheses are: 1) mechanisms which allow B. pseudomallei to resist killing by ROS and RNS are critical for survival during disease and are thus logical candidates for antimicrobial intervention and 2) resistance proteins are highly expressed during disease and thus ideal candidates for vaccine development. We will study B. pseudomallei's adaptation to oxidative and nitrosative stress using global expression profiling methods refined in our studies of Mycobacterium tuberculosis. We will identify the transcriptional response of B. pseudomallei to ROS and RNS, determine the role of the major oxidative stress regulators (OxyR and SoxR) in defense against ROS and RNS, and identify key resistance proteins for vaccine and drug development. Project interactions In addition to the interactions described in this proposal with other project members (e.g. Drs. Vasil, Holmes, & Vazquez-Torres), we will interact with Dr. Slayden (Genomics/Proteomics Core-CSU) in the development and use of microarray technology and the evaluation of potential target proteins for therapeutic agents, Dr. Robinson (Select Agent Archive-BYU) for access to representative B. pseudomallei isolates, and Dr. Schweizer (Microbial Genetics-CSU) in terms of genetics of B. pseudomallei.